|Type I barriersa||6d||102||419||44||87||34||47||114||1,146|
|Type II barriersb||0||70||128||19||32||15||31||22||391|
|All other typesc||N||2||28||0||6||0||1||1||79|
|Cost (1998 $ millions)||N||134||656||89||152||60||111||169||1,931|
a A Type I barrier is built on a highway project to construct a new highway or to physically alter an
b A Type II barrier is built to abate noise along an existing highway (often referred to as retrofit abatement) and is not mandatory.
c All other types of barriers are nonfederally funded.
d Have not been assigned a year of construction or a cost.
KEY: N = data do not exist; R = revised.
NOTES: Miles have been converted from kilometers. Totals may not match the sum of yearly estimates due to rounding and converting from metric. 24 miles of barriers, while assigned a year of construction, cannot be assigned a cost. Data are produced on a 3-year cycle.
SOURCE: U.S. Department of Transportation, Federal Highway Administration, Office of Environment and Planning, HighwayTraffic Noise Barrier Construction Trends (Washington, DC: 2000), tables 1 and 3.